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Planetesimal Hypothesis

a theory advanced by Chamberlin and Moulton to explain the origin of the solar system consistently with what has more recently been discovered of the prevalent forms and forces still apparently at work in the outer universe. According to this theory the solar system was evolved from a great spiral nebula similar to the thousands upon thousands of such nebulæ that the telescope has brought to light in recent years. The elements of the nebula were fine particles of solid or liquid matter called planetesimals, out of which, as they traveled in their orbits around a central mass, were formed larger and larger aggregates of matter, namely, the future earth and other planets, while the central mass became the sun as we know it. According to this hypothesis, meteors are portions of matter still being gathered in from the original disruption of the sun or giant star out of which was formed the original nebula. Other applications of the theory have to do with the internal heat of the earth, the formation of the atmosphere, and the origin of the earth's oceans.

The theory is consistent with many of the facts brought to light by geological investigations as well as with astronomical discoveries. a PNEUMATIC BREAKWATERS, system of breaking the force of ocean waves invented by Philip Brasher and now used in the protection of several exposed piers on the Pacific coast. Per- PROHIBITION forated pipes connected with compressed air tanks are laid under water at the proper depths and beyond the pier to be protected. The rising of the wall of air bubbles through the water breaks the force and onward motion of the waves in much the same way as a shoal or submerged sandbar would do, and one great advantage of the air breakwater is that it forms no obstacle to navigation even when operating in storms.

POISON GAS TREATY. (See WASH- INGTON CONFERENCE.) POLAND. New constitution adopted March 17, 1921. Parliament of two chambers elected by popular vote, malo and female. President elected by National Assembly and may be either Catholic or Protestant. In time of war, military responsibility shifts to Secretary of War. Equal rights to all religions. Free compulsory education. Freedom of language to all nationalities. Land holdings restricted, and other provisions include the care of orphans by the state and the prohibition of night work by women.

March 18, 1921, treaty with Russia, in which Russia agreed to return expropriated property, to extend the Polish boundary, and to pay indemnity of thirty million rubles. Mutual abstention from propaganda. Polish-Lithuanian dispute over Vilna. (See VILNA, below.) PORTO RICO. (See UNITED STATES, 1921-1922.) PORTUGAL. This country was the scene of many political disturbances due to the revolutionary activities of secret societies among them the "Thirteen Club." On October 19, 1921, came an outbreak at Lisbon, in which the Premier and prominent supporters of his government were killed. A new cabinet was formed by Da Silva.